ELECTRICAL ASSESSMENT OF AQUIFERS IN THE BASEMENT COMPLEX OF UNILORIN: IMPLICATIONS FOR EXISTING BOREHOLES
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Date
2015
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School of Science and Technology Education, Federal University of Technology, Minna
Abstract
Schlumberger 4-electrode array was employed to sound 21 stations. IPI2WIN and Surfer12 software were used to infer lithological series, aquifer thickness, and depth. The aquifer hydraulic conductivity K and transmissivity T were calculated from the VES data using the Dar Zarouk principles. The field curves show that the area has 3 and 4 geo-electric layers. The layers were interpreted as the topsoil (130- 1469 Ωm), clayey (wet to dry) (52.6 – 8552 Ωm), weathered/fractured basement (46.2- 249 Ωm), and fresh basement (454- 5022 Ωm) respectively. The aquiferous zones lie within the second and third layers. The aquifer depth is between 6.17 m and 24.9 m while the thickness ranges from 1.89 to 22.7 m. The longitudinal conductance S ranges from 0.02 to 0.468 Ω-1 and transmissivity T varies from 246 to 2419.8 Ωm2. The results confirmed the functionality of boreholes, such as VES3, sited in areas with maximum aquifers and highest transmissivity T. The NE and NW parts were found most suitable for freshwater exploitations. Low longitudinal conductance which implies low protective cover, in the vicinity of the borehole near VES 6 suggests the contamination claim of its water.
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Keywords
Aquifer, Borehole, Hydraulic Conductivity and Transmissivity., Research Subject Categories::NATURAL SCIENCES